The present invention relates generally to semiconductor devices, and more particularly, to a semiconductor device having a metal wiring layer which utilizes a dummy metal pattern to enhance the corrosion-resistance and reliability thereof.
As semiconductor technology continues to evolve towards higher integration density devices, the width of the metal lines of the metal wiring layer thereof continues to be reduced or thinned. This thinning of the metal lines degrades the reliability of the metal wiring layer. More particularly, thinner metal lines are especially susceptible to destructive corrosion which can occur when the metal wiring layer is exposed to air following a reactive ion etching (RIE) process carried out in a plasma containing chlorine (Cl) or other type of caustic etchant. The corrosion is caused by residual chlorine or chlorine compounds left on the wafer surface of the semiconductor device following the etching process reacting with moisture in the air and thereby hydrolyzing to form hydrochloric acid (HCI). The hydrochloric acid corrodes weak or unprotected portions of the sidewalls of the metal lines where a protective native oxide has been incompletely formed. Corrosion proceeds rapidly as a result of this electrochemical reaction. If the metal bonding pad portions of the metal wiring layer are corroded, then the bondability of the semiconductor device will be degraded, and if the metal line pattern of the metal wiring layer is corroded, the likelihood of open lines and thus, failure of the semiconductor device is dramatically increased. Thus, it can be appreciated that corrosion of the metal bonding pads and/or the metal lines of the metal wiring layer of a semiconductor device can significantly degrade the performance and reliability of the device.
One technique which has been proposed to alleviate the above-described metal wiring layer corrosion problem is to replace chlorine (Cl) radicals formed during the RIE process utilizing a chlorine-containing plasma, with fluorine (F) radicals, by utilizing a fluorine-containing plasma such as CF.sub.4 in place of the chlorine-containing plasma. Using this technique, instead of chlorine radicals being formed on the sidewalls of the metal lines and bonding pads of the metal wiring layer, fluorine radicals are formed thereon. The fluorine radicals are generally less reactive with the metal, e.g., aluminum (Al) or aluminum alloy (e.g., Al-1%Si, Al-1%Si-0.5%Cu), of the metal wiring layer, and thus, less corrosive. In one variation of this technique, a CHF.sub.3 RIE plasma is used, to thereby form a chemically stable AIF.sub.3 protective coating on the surface of the metal wiring layer, thereby further minimizing corrosion thereof.
However, the above-described technique requires that the etching process parameters (e.g., time, pressure, temperature, amount of etchant gas, magnitude of external power source, thickness and composition of photoresist, etc.) be tightly controlled, and therefore, unduly complicates the manufacturing process. Moreover, this technique has proven not to be entirely effective in eliminating the corrosion problem. Additionally, this technique is difficult to control to the extent required to maintain precise control over the geometry of the metal wiring layer, e.g., the uniformity of the width and spacing of the metal lines thereof. Because of these non-uniformities, the protective layer formed on the sidewalls of the metal lines and bonding pads of the metal wiring layer are also non-uniform, thereby resulting in local corrosion thereof. This local corrosion phenomenon is depicted in FIG. 1, where the white lines represent aluminum metal lines of the metal wiring layer of a semiconductor device. As can be seen, the local corrosion phenomenon causes a break or opening of one of the metal lines at a point indicated by the reference character A. This local corrosion phenomenon is also depicted in FIG. 2, where it can be seen that the one of a plurality of parallel metal lines adjoining a wide open area is broken at a point indicated by the reference character B.
Based upon the foregoing, it is evident that there presently exists a need for a semiconductor device having a metal wiring layer which overcomes the deficiencies of the metal wiring layer of presently available semiconductor devices. The present invention fulfills this need.